Thesis (Ph.D.)--University of Arizona, 2006 / Includes bibliographical references (p. 246-257). Also available via the Internet.

Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Committee Chair: Judith Curry; Committee Chair: Peter J Webster; Committee Member: Marc Stieglitz; Committee Member: Robert Black; Committee Member: Rong Fu.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 104-106). Also available via the Internet.

Thesis (M.S.)--Oregon State University, 1991. / Typescript (photocopy). Includes bibliographical references (leaves 84-90). Also available on the World Wide Web.

Magister Scientiae - MSc / The aim of this research project was to estimate parameters for the distribution of annual maximum flood levels for the Zambezi River at Katima Mulilo. The estimation of parameters was done by using the maximum likelihood method. The study aimed to explore data of the Zambezi's annual maximum flood heights at Katima Mulilo by means of fitting the Gumbel, Weibull and the generalized extreme value distributions and evaluated their goodness of fit. / South Africa

Temporal and spatial variations of the Fraser River plume, in the central Strait of Georgia (British Columbia, Canada), are monitored by continuous salinity sampling of the engine cooling water on two B.C. ferries. Travelling along two different routes between Vancouver Island and the mainland the ferries provide eight crossings per day both north and south of the river outflow. From each crossing, characteristic measures of the plume are extracted, such as the average salinity and the maximum salinity gradient. These parameters are then formulated as time series and used to compute cross-correlations and cross-spectra with the probable driving forces of wind and river discharge. The effect of the tides is examined using harmonic analysis. Periods of high river discharge lead to decreases in the average salinity for each section, and peaks in the magnitude of the maximum salinity gradient. The correlation of the plume characteristics (average salinity, maximum salinity gradient) on the southern section with the along-strait component of the wind is consistent with advection by the wind. Weak correlation is found between the plume characteristics on the northern section and the wind. Linear combination of the wind and the discharge variations reproduce the general trend of the average salinities but cannot explain the level of variability. A shift to a nonlinear combination of the wind and discharge improves this comparison. The phases of parameter fluctuations at tidal frequencies, on the southern section, agree with the expected effects of tidal currents and the modulation of the river discharge. The agreement is not as apparent for the northern section. The level of the discharge is seen to affect the tidal amplitudes of the salinity fluctuations on the southern section. A numerical model, previously developed to examine the effect of tidal forcing on the plume, is modified to input the hourly wind and daily discharge data record. Equivalent average salinities along the ferry section are outputed and compared to the observed ferry data. Good agreement is reached after manipulating the entrainment velocity and the momentum transfer from the wind to the plume. The tides are seen to add a tidal modulation to the general salinity pattern resulting from the combined effect of the wind and the discharge. Horizontal distributions from the model and from CTD cruise results agree fairly well with each another. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Oxygen transfer between flowing surface waters and the atmosphere can be mathematically described as a first-order reaction and is known as stream reaeration. The first-order rate coefficient or stream reaeration coefficient is a necessary input parameter to stream water-quality models and is partially controlled by the hydraulic conditions of the stream. These coefficients may vary for a given stream reach because of varying hydraulic characteristics brought about by streamflow changes. Hydraulic measurements and reaeration coefficient determinations were made on four pool-and-riffle reaches of Middle Fork Beargrass Creek near Louisville, Kentucky using the hydrocarbon gas tracer technique. Measurements were made on each reach for up to seven streamflow conditions ranging from extremely low to medium. Contrary to published findings applicable to reaches not characterized by a series of pools and riffles, the reaeration coefficient was shown to increase with increasing streamflow for all four reaches studied. Therefore, stream water-quality models developed for these, or similar, stream reaches using reaeration coefficients determined at normal streamflow conditions may over estimate the influence of atmospheric reaeration under a much lower flow condition, such as extreme low flow--the selected critical condition for which water-quality models are commonly developed. Twenty-five published equations used for estimating stream reaeration coefficients were evaluated using the measured hydraulic and reaeration data and were shown to generate highly variable and generally inaccurate predictions. Over half of the equations generated mean prediction errors of more than 50 percent. The best equation overall generated a mean prediction error of 15 percent. The equations were also shown to be highly sensitive to the methods used for determining the input parameter values. Four equations were statistically developed from the data collected in this research. Two of the equations provided more accurate estimates for the four studied reaches than any of the 25 published equations. Mean prediction errors for the two were 1.2 and 9.2 percent. For verification, the developed equations were also evaluated against the 25 published equations using published reaeration and hydraulic data from 39 hydrocarbon gas tracer measurements on other streams. The two developed equations which were most accurate for the four study reaches were also determined to be superior to all of the 25 published equations using the verification data. Mean prediction errors for the two equations using the verification data were 2.3 and 5.5 percent. / Ph. D.

Text in Afrikaans / Water is in 'n relatief droe land soos Suid-Afrika van uiterste belang. Daar is 'n groot behoefte aan inligting oor die potensieel verbruikbare waterbronne. Hierin word voorsien deur 'n netwerk van riviervloeimeetstasies. Met veranderende ekonomiese toestande word die effektiwiteit van die netwerk van al hoe groter belang. Dit is hier waar netwerkbeplanning 'n aktiewe rol begin speel. As gevolg van die groot variasie in die aard van die opvanggebiede in Suid-Afrika, en die feit dat daar 'n bestaande netwerk is, is dit nodig dat netwerkbeplanning stapsgewys benader word. Die Eerste Fase is 'n leerproses. Die verskillende opvanggebiede in die land kan gegroepeer word en die meetstasies kan geklassifiseer word. 'n Netwerkbeplanningsmetode, "Die ideale netwerk", is ontwikkel en word op drie opvanggebiede toegepas. Die belangrikste resultaat is die klassifikasie van al die meetstasies in die drie opvanggebiede. / In a relative dry country like South Africa water is of critical importance. Information on the potential usable water resources is very valuable. This information is supplied by a network of river flow gauging stations. In changing economic times the effectiveness of this network is of increasing importance. Network design plays a major role in insuring this. Network design has to be approached in phases because of the variety in catchment characteristics in South Africa, and the fact that there is an existing network. The First Phase can be regarded as a learning phase, in which all the catchments in the country can be grouped and the stations can be classified. A network design method, · "The ideal network", was developed, and is applied in three catchments. The most important result is the classification of all the existing stations in the three catchments. / Geography / M. Sc. (Geografie)

The aim of this research project was to estimate parameters for the distribution of annual maximum flood levels for the Zambezi River at Katima Mulilo. The estimation of parameters was done by using the maximum likelihood method. The study aimed to explore data of the Zambezi's annual maximum flood heights at Katima Mulilo by means of fitting the Gumbel, Weibull and the generalized extreme value distributions and evaluated their goodness of fit.

The existing theories for predicting longitudinal dispersion in straight open channels have long been recognized as inadequate when applied to natural rivers. These theories tend to grossly underestimate dispersion in real streams since an important mixing mechanism due to nonuniform river cross-section variations is not explicitly taken into account. Recognizing the important role of stream irregularities on solute transport and the analytical difficulties of classical deterministic analysis, we develop a stochastic approach for analyzing solute transport in natural streams. Variations in river width and bed elevation are conveniently represented as one-dimensional random fields, characterized by their autocorrelation functions. Advection and dispersion due to the combined effect of turbulent diffusion and nonuniform flow are described by the stochastic solute transport equation. When boundary variations are small and statistically homogeneous, a stochastic spectral technique is used to obtain closed-form stochastic solutions. In particular, closed-form expressions are obtained for effective mean solute transport velocity and effective dispersion coefficient reflecting mixing due to flow variations both within the river cross-section and in the streamwise direction. The results show that the mean behavior of solute transport in a statistically irregular stream can be described as a gradient dispersion process. The effective mean transport velocity in natural rivers is smaller than that in a corresponding uniform channel, and the effective longitudinal dispersion coefficient in natural rivers can be considerably greater than that of uniform open channels. The discrepancy between uniform channels and natural rivers increases rapidly as the variances of river width and bed elevation increase, especially when the mean flow Froude number is high.